Refrigerant leak detection system and method

ABSTRACT

Disclosed is a system for detecting a refrigerant leak in a refrigeration system, wherein a system controller is configured to: execute leak test cycles that include executing a first phase (T 1 -T 2 ) of transferring refrigerant charge to the evaporator, a second phase (T 2 -T 3 ) of transferring refrigerant charge to the condenser, and a third phase (T 3 -T 4 ) of transferring refrigerant charge to the evaporator, determine a reference leak detection cycle time (LDCTREF) by determining a time from a beginning of the second phase (T 2 ) in a first test to an end of the third phase (T 4 ) in the first test, and setting LDCTREF to the time, determine a second leak detection cycle time (LDCT 2 nd) by determining a time from a beginning of the second phase (T 2 ) in the second test to a second end of the third phase (T 4 ) in the second test, and setting LDCT 2 nd to the time, determine if a refrigerant leak exists, and communicate the determination.

BACKGROUND

Exemplary embodiments pertain to the art of maintenance of arefrigeration systems and more specifically to a system and method fordetecting a refrigerant leak in a refrigeration system.

There are two typical methods of detecting a refrigerant leak inrefrigeration unit. A first method may be detecting leaking gas in aspace surrounding the refrigeration unit. This method may be limited dueto air movement around units and positions of gas sensors. In outdoorsituations, this method may be very inaccurate. A second method mayapply analytics of operational parameters such as pressures andtemperatures within the unit. Inaccurate modeling and non-steady stateoperation of the units may make this method inaccurate and ineffectiveuntil as much as 20% of total refrigerant charge is depleted.

BRIEF DESCRIPTION

Disclosed is a system for detecting a refrigerant leak in arefrigeration system, the refrigeration system including a refrigerantcharge, an evaporator, a condenser and a system controller, wherein thecontroller is configured to: execute a plurality of leak test cycles,including a first leak test cycle and a second leak test cycle, each ofthe plurality of leak test cycles comprising executing a first phase oftransferring the refrigerant charge to the evaporator, executing asecond phase of transferring the refrigerant charge to the condenser,and executing a third phase of transferring the refrigerant charge tothe evaporator, determine a reference leak detection cycle time(LDCTREF) by determining a first time from a first beginning of thesecond phase in the first leak test cycle to a first end of the thirdphase in the first leak test cycle, and setting LDCTREF to the firsttime, determine a second leak detection cycle time (LDCT2nd) bydetermining a second time from a second beginning of the second phase inthe second leak test cycle to a second end of the third phase in thesecond leak test cycle, and setting LDCT2nd to the second time,determine if a refrigerant leak in the refrigeration system exists ifLDCT2nd is shorter in duration than LDCTREF, and communicate anexistence of the refrigerant leak with an alert which is one or more ofvisual, audible, and vibratory.

In addition to one or more of the above disclosed features, or as analternative, the first phase initiates with the controller taking therefrigeration system off line.

In addition to one or more of the above disclosed features, or as analternative, the third phase concludes with the control bringing therefrigeration system on line.

In addition to one or more of the above disclosed features, or as analternative, the controller periodically performs one of the pluralityof leak detection test cycles.

In addition to one or more of the above disclosed features, or as analternative, the controller performs the one of the plurality of leakdetection test cycles following a non-periodic trigger event.

In addition to one or more of the above disclosed features, or as analternative, the trigger event includes the controller bringing therefrigeration system off line for maintenance.

In addition to one or more of the above disclosed features, or as analternative, the refrigeration system includes a variable speedcompressor and an electronic expansion valve (EXV), and wherein thefirst phase starts at time T1 and ends at time T2 as monitored by thecontroller, and throughout the first phase the controller sets thecompressor to minimum output and the EXV to maximum opened, and thecontroller monitors pressure in at least one of the condenser andevaporator to determine when the evaporator is charged with the systemrefrigerant and the compressor is empty of system refrigerant.

In addition to one or more of the above disclosed features, or as analternative, the second phase starts at time T2 and ends at time T3 asmonitored by the controller, and throughout the second phase thecontroller sets the compressor to no output and sets the EXV to closed,and the controller monitors pressure in at least one of the condenserand evaporator to determine when the condenser is charged with thesystem refrigerant and the evaporator is empty of system refrigerant.

In addition to one or more of the above disclosed features, or as analternative, the third phase starts at time T3 and ends at time T4 asmonitored by the controller, and throughout the third phase thecontroller sets the compressor to no output and sets the EXV to maximumopened, and the controller monitors pressure in at least one of thecondenser and evaporator to determine when the evaporator is chargedwith the system refrigerant and the compressor is empty of systemrefrigerant.

In addition to one or more of the above disclosed features, or as analternative, the controller monitors evaporator suction pressure todetermine when the evaporator is empty of system refrigerant.

Further disclosed is a method for detecting a refrigerant leak in arefrigeration system that includes one or more of the above disclosedfeatures.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 illustrates features of a disclosed embodiment;

FIG. 2 illustrates features of a disclosed embodiment;

FIG. 3 illustrates features of a disclosed embodiment;

FIG. 4 illustrates features of a disclosed embodiment;

FIG. 5 illustrates features of a disclosed embodiment;

FIG. 6 illustrates features of a disclosed embodiment;

FIG. 7 illustrates features of a disclosed embodiment;

FIG. 8 illustrates features of a disclosed embodiment;

FIG. 9 illustrates features of a disclosed embodiment; and

FIG. 10 illustrates features of a disclosed embodiment.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

According to an embodiment, an approach to detect refrigerant leak isprovided that is based on an automated transient process for operating arefrigeration circuit. In a disclosed mode of operation, a first amountof refrigerant present inside the refrigeration circuit may beestimated, where the estimate is relatively accurate compared withtypical commercially practiced methods. By benchmarking the first amountas a normal amount of refrigerant, an estimation of a later amount ofrefrigerant in the same circuit may provide for a detection of a missingfraction of the refrigerant in the circuit.

Turning to FIG. 1 , a refrigerant circuit 100 is illustrated in a normaloperational mode, where the operational mode is controlled by acontroller 102. The refrigerant circuit includes a condenser 104 and anevaporator 108 disposed below the condenser. During operation, thecondenser may have a first portion of the refrigerant in the systemwhich includes a first gas portion 112 and a first liquid portion 116.At the same time the evaporator may have a second portion of the systemrefrigerant including a second gas portion 120 and a second liquidportion 124.

A first fluid path 128 with a compressor 132 fluidly connects thecondenser with the evaporator. In the first path, refrigerant may flowfrom the evaporator to the condenser by action of the compressor. Forpurposes of this disclosure, the compressor, which is a variablecapacity compressor, may operate in a range between a minimum outputstate 136 and a maximum output state 140 and the compressor may also bein a stopped or idle state 142. In some cases several compressorsoperating in parallel may operate in a same refrigerant circuit.

A second path 148 with an electronic expansion valve (EXV) 152 alsoconnects the condenser with the evaporator. In the second path,refrigerant may flow from the condenser to the evaporator by action of apressure differential between condenser and evaporator and a flow ofrefrigerant is controlled by action of the EXV. The EXV may operate in arange between a maximum opened state 160 and a closed state 156,illustrated respectively as 100% closed and 0% opened. The EXV mayoperate in a first EXV state 164, which may be one of many normal statesbetween the closed state 160 and the maximum opened state 156.

The disclosed embodiments may create an artificial transient mode ofoperation for estimating refrigerant charge. This mode of operation maybe divided into various phases. As illustrated in FIG. 9 , with T0-T4representing time, curve 200 may represent the operation of the EXV,curve 204 may represent the operation of the compressor, curve 208 mayrepresent the pressure in the evaporator, and curve 212 may representpressure in the compressor. T0-T1 may represent the operation of thesystem prior to running a leakage test, and T1-T4 may represent theoperation of the system during a leakage test. More specifically, T1-T2may represent the operation of the system during the first phase of theleakage test, T2-T3 may represent the operation of the system during thesecond phase of the leakage test, and T3-T4 represents the operation ofthe system during the third phase of the leakage test.

Referring to FIGS. 1 and 9 , during normal operation, between time T0and T1, the compressor may be running in the first compressor state 144,the EXV may be operating in the first EXV state 164, pressure in theevaporator PE may remain approximately PE1 and pressure in the condenserPC may remain approximately PC1. During normal use, the flow rate ofrefrigerant may be substantially constant in all components.

Referring to FIGS. 2, 7 and 9 , during the first phase, a maximum amountof system refrigerant may be delivered to the evaporator. Specifically,at step S100 and time T1, the controller may initiate the first phase.At step S104 and time T1, the controller may take the system off line soas to not interfere with active cooling cycles. At step S108 and timeT1, the EXV may be opened to the maximum opened state 156 and thecompressor capacity (volumetric flow) may be brought to the minimumoutput 136. At step S112 and between time T1 and time T2, that is,throughout the first phase, the controller may monitor refrigerantconditions. During this time, the controller may also perform step S116of determining whether a maximum amount of available refrigerant isdisposed in the evaporator. At time T2, which may define the end of thefirst phase, pressure in the condenser may reach PC2 and pressure in theevaporator may reach PE2, and the determination may be “Yes” at stepS116. The duration of this phase may be determined by a detection ofsteady state operation (that is, reaching values of constant pressuresin the evaporator and the condenser) or based on a predetermined timeduration based on theoretical determinations or prior actualobservations (for instance two minutes). In one embodiment, the firstphase may take approximately two minutes to complete when the system isfully charged and when not fully changed.

Referring to FIGS. 3, 4, 7 and 9 , at step S118 and time T2, thecontroller may initiate the second phase, which may be transferring therefrigerant from the evaporator to the condenser. At step S120 and T2,the controller may put the EXV in the closed state 160 and put thecompressor in the minimum transfer state 136 as illustrated in FIGS. 3and 9 . At step S124 and between time T2 and T2, that is, throughout thesecond phase, the controller may monitor refrigerant conditions. Duringthis time, the controller may perform step S128 of determining whether amaximum available refrigerant is disposed in the condenser. At time T3,which may define the end of the second phase, pressure in the condensermay reach PC2 and pressure in the evaporator may reach PE2, and thedetermination may be “Yes” at step S128. In one embodiment, the secondphase may take approximately three minutes to complete when the systemis fully charged.

In one embodiment, the evaporator suction pressure may be monitored todetermine when the evaporator is empty. Moreover, as the compressorprovides a constant refrigerant volumetric flow, the time needed totransfer refrigerant from evaporator to condenser (when the EXV isclosed) may be a function of an amount of refrigerant stored inevaporator. To better assess the amount of refrigerant transferredduring this phase, a real time calculation of refrigerant density may beperformed by the controller and this may be taken into account tocalculate a mass of refrigerant transferred.

Referring to FIGS. 5-7 and 9 , at step S132 and time T3, the controllermay initiate the third phase of transferring the refrigerant back to theevaporator. At step S136 and time T2, the controller may place thecompressor in the stopped state 142 and place the EXV in the maximumopened state 156. At step S140 and between time T3 and T4, that is,throughout the third phase, the controller may monitor refrigerantconditions. During this time, the controller may perform step S144 ofdetermining whether a maximum available refrigerant is disposed in theevaporator. At time T4, which may define the end of the third phase,pressure in the condenser may reach PC4 and pressure in the evaporatormay reach PE4, and the determination may be “Yes” at step S144. In oneembodiment, the third phase may take about 2 minutes to complete whenthe system is fully charged.

As indicated, at the start of the third phase, almost all availablerefrigerant may be stored in the condenser, which may be mostly liquidat a relatively high pressure, while the evaporator may be at arelatively low pressure. During this phase the EXV may be considered afixed geometry orifice. Due to the pressure difference, all refrigerantstored in the condenser may flow to the evaporator. The transfer timemay be a function of geometry, that is, of the orifice dimension, andthe amount of refrigerant transferred. As illustrated, PE4 and PC4 maybe substantially equal at time T4.

At step S148 the controller may determine the duration between T2 andT4, that is, the start of the second phase and the end of the thirdphase. This time may represent the duration of (i) the time needed totransfer refrigerant from evaporator to condenser with the compressoroperating at minimum output and with the EXV closed and (ii) the timeneeded to transfer refrigerant from the condenser back to the evaporatorwith the compressor stopped and the EVX in a maximum opened state. Thistime period is the leak detection cycle time (LDCT). At step S152, thecontroller may put the refrigerant system back online. The LDCT may bebased on transfer time corresponding to each phase or may be based onmore sophisticated function which will take into account variation ofrefrigerant density (calculated in real time by controller) during giventransfer phase.

Referencing FIGS. 8 and 9 , at step S180 the first LDCT measurement isset by the controller as a reference transfer time (LDCT-REF). Thistransfer time essentially corresponds to the transfer of the totalrefrigerant charge between the evaporator and condenser.

At step S184 the controller may perform leak detection testing after thefirst test. At step S186 the controller may determine whether to performa periodic test, such as a time of day or week. At step S188 thecontroller may determine whether to perform a non-periodic leakdetection test based on a trigger event. The trigger event could betaking the system off line for a non-critical reason, such as formaintenance, during the normal useful life of the system. The order ofexecuting steps S186 and S188 is not limiting. So long as the controllerdetermines “No” for steps S186 and S188, the system will cycle todetermine whether to execute a leak detection test.

Upon determining “Yes” at steps S186 or S188, the controller may executestep S192 of performing a leak detection test, which is repeating thefirst through third phases. Referencing to FIGS. 8 and 9 , ifrefrigerant is leaked, then during the second phase the condenser willreach pressure PC3 and the evaporator will reach pressure PE3 at timeT3A, which is shorter than T3. Similarly, with a leak, during the thirdphase the condenser will reach pressure PC4 and the evaporator willreach pressure PE4 at time T4A, which is shorter than T4.

At step S196 at time T4, the controller may set the LDCT determinedduring the immediately preceding cycle as LDCT_(CUR) and compare it withthe reference time LDCT_(REF). The controller may also sequentiallynumber each recorded LDCT so that, for example the second recorded LDCTmay be recorded by the controller as LDCT_(2nd). If LDCT_(CUR) is lessthan LDCT_(REF), then a leak has been detected. At step S200 if thecontroller determines “No”, for example, that no leak has been detected,then the controller may cycle back to step S184. Otherwise, if theresult of step S200 is “Yes”, then at step S204 the system may set offan alert, which may be visual, auditory, and/or vibratory indicating aleak has occurred. In one embodiment the system cycles back to step S184to continue to test for leaks, the results of which may be indicative ofa leak rate when compared with the earlier detection.

A normal method of detecting leaks in a refrigerant system may notdetect leaks until a substantial amount of refrigerant is lost. However,as illustrated in FIG. 10 , the disclosed embodiments may detect leaksat for example approximately 5% refrigerant loss. For example, a scattergraph 220 representing a ratio of LDCT_(CUR) to LDCT_(REF) may detect aloss of a few percentages of refrigerant over various days, which asillustrated is 5 percentage points. It is to be appreciated that quicklyidentifying losses may enable quickly fixing systems and may avoiddisruptions and system damage.

The term “about” is intended to include the degree of error associatedwith measurement of the particular quantity based upon the equipmentavailable at the time of filing the application. The terminology usedherein is for the purpose of describing particular embodiments only andis not intended to be limiting of the present disclosure. As usedherein, the singular forms “a”, “an” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, element components,and/or groups thereof.

While the present disclosure has been described with reference to anexemplary embodiment or embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe present disclosure. In addition, many modifications may be made toadapt a particular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof. Inparticular only one of the detection phases may be used during thedetection process (for instance only phase 2 corresponding to thetransfer from the evaporator to the condenser, or only phase 3corresponding to the transfer from the condenser to the evaporator).Therefore, it is intended that the present disclosure not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this present disclosure, but that the present disclosurewill include all embodiments falling within the scope of the claims.

1-10. (canceled)
 11. A method for detecting a refrigerant leak in arefrigeration system, the refrigeration system including a refrigerantcharge, an evaporator, a condenser and a system controller, wherein thecontroller: executes a plurality of leak test cycles, including a firstleak test cycle and a second leak test cycle, each of the plurality ofleak test cycles comprising executing a first phase of transferring therefrigerant charge to the evaporator, executing a second phase oftransferring the refrigerant charge to the condenser, and executing athird phase of transferring the refrigerant charge to the evaporator,determines a reference leak detection cycle time by determining a firsttime from a first beginning of the second phase in the first leak testcycle to a first end of the third phase in the first leak test cycle,and setting the reference leak detection cycle time to the first time,determines a second leak detection cycle time by determining a secondtime from a second beginning of the second phase in the second leak testcycle to a second end of the third phase in the second leak test cycle,and setting the second leak detection cycle time to the second time,determines if a refrigerant leak in the refrigeration system exists ifthe second leak detection cycle time is shorter in duration than thereference leak detection cycle time, and communicate an existence of therefrigerant leak with an alert which is one or more of visual, audible,and vibratory.
 12. The method of claim 11 wherein the first phaseinitiates with the controller taking the refrigeration system off line.13. The method of claim 11, wherein the third phase concludes with thecontrol bringing the refrigeration system on line.
 14. The methodaccording to claim 11, wherein the controller periodically performs oneof the plurality of leak detection test cycles.
 15. The method accordingto claim 11, wherein the controller performs the one of the plurality ofleak detection test cycles following a non-periodic trigger event. 16.The method of claim 15 wherein the trigger event includes the controllerbringing the refrigeration system off line for maintenance.
 17. Themethod according to claim 13, wherein the refrigeration system includesa variable speed compressor and an electronic expansion valve, andwherein the first phase starts at a time T1 and ends at a time T2 asmonitored by the controller, and throughout the first phase thecontroller sets the compressor to minimum output and the electronicexpansion valve to maximum opened, and the controller monitors pressurein at least one of the condenser and evaporator to determine when theevaporator is charged with the system refrigerant and the compressor isempty of system refrigerant.
 18. The method of claim 17, wherein thesecond phase starts at the time T2 and ends at a time T3 as monitored bythe controller, and throughout the second phase the controller sets thecompressor to no output and sets the electronic expansion valve toclosed, and the controller monitors pressure in at least one of thecondenser and evaporator to determine when the condenser is charged withthe system refrigerant and the evaporator is empty of systemrefrigerant.
 19. The method of claim 18, wherein the third phase startsat the time T3 and ends at a time T4 as monitored by the controller, andthroughout the third phase the controller sets the compressor to nooutput and sets the electronic expansion valve to maximum opened, andthe controller monitors pressure in at least one of the condenser andevaporator to determine when the evaporator is charged with the systemrefrigerant and the compressor is empty of system refrigerant.
 20. Themethod according to claim 19, wherein the controller monitors evaporatorsuction pressure to determine when the evaporator is empty of systemrefrigerant.